Electronic devices supplied with energy by an external voltage source, such as a smart card, for example, which is supplied with energy via a supply contact by a reader into which said card is inserted, typically include a voltage regulator that converts the external supply voltage into an internally required supply voltage. Efficient voltage converters are desirable which for example can be implemented with little outlay (e.g. with small area requirement) and react for example rapidly to fluctuations in the external supply voltage.